The estimates of what % of the U.S. population are millionaires varies, but I was using roughly 5%. So if 95% of the population (non-millionaires) drives 86% of luxury cars, and the remaining 5% drives 14% of luxury cars, that means that the luxury car prevalence ratio among nonmillionaires:millionaires is (86/95):(14/5) = ~1:3.